1. Field of the Invention
The invention relates to a process and apparatus for laying fiber bands of filaments by changeably moveable weft layers or diagonal layers to form fiber arrangements stretched in different laying directions between two transport devices equipped with guide hooks and retainer hooks and thus conveyed to a pretreatment station. The endless flat fiber bands are spread individually, and guided by guide elements of the weft layer or diagonal layer aligned perpendicular to the preset laying direction crosswise over both transport chains and deposited. Each of the fiber bands is guided by a guide element that crosses the row of guide hooks of the transport chain to respectively form a direction change fold having a lower strand, an upper strand and an apex, such that the fiber band is inserted into retainer elements.
2. Discussion of Background Information
A method of the type mentioned was proposed through DE 101 49 161 C2. The sheet of fiber bands is guided diagonally over the transport chains with the aid of a weft layer or a diagonal layer. The guide elements for the fiber bands are aligned perpendicular to the movement direction of the weft layer and arranged in a line next to one another parallel to the transport chains. The transport chains have two rows of hooks arranged spaced at a distance from one another. The guide hooks are located adjacent to the fiber arrangement. They have perpendicular needles closely adjacent to one another with the tip pointing upwards. Outside this row of guide hooks there is another row with retainer needles pointing upwards and outwards. These are likewise arranged very densely.
The guide elements on the weft layer or diagonal layer are vertically fixed. In the direction change phase a so-called fold tensioner is inserted behind the guide element of the weft layer, which fold tensioner guides the upper and lower strands of the direction change fold separately from one another at the apex of the same until both strands are transferred to the row of guide hooks again after racking of the upper strand is completed by a racking grid swung in from above. While racking is executed, the fibers of the direction change fold are stretched and collected by a so-called loop tensioner and transferred to the row of retainer hooks in the form of a rope.
Due to the large number of tools involved in the operation, this procedure requires a very high control expenditure. The desired effect, namely to achieve a really gap-free form of the fiber arrangement, is achieved only with reservations. The working speed remains limited and is unsatisfactory. With a change in the width of the fiber bands or with the change of alignment of the fiber band sheet between the transport chains, the work elements always have to be structurally adapted to the new conditions. The associated expense is high.
With DE 197 42 721 C1 a method and a device for laying and positioning weft thread sheets is known in which the transport chains are likewise equipped with guide hooks and needle-shaped retainer hooks. The weft thread layer is lowered in connection with a presser rail outside the retainer hooks under the tips of the same after it has executed a first racking. After completion of a further final racking under the tips of the retainer hooks, the weft thread guide is raised again and lays the weft thread sheet, which is now stretched between the retainer hooks and the weft thread guide, at a predetermined point into the row of the guide hooks of the transport chains.
However, with this mode of operation and this device only weft thread sheets, the weft threads of which are not laterally connected to one another can be reliably hooked into the transport chains. This mode of operation is not suitable for fiber bands of, e.g., carbon or glass filaments, in which the filaments are held against one another in a predetermined defined position, namely forming a band, by adhesive materials. During racking the cross sections of the fiber band are raised in an uncontrolled manner, so that a uniform hooking, in particular of the upper strand, into the row of guide hooks cannot be guaranteed. In addition, during the racking of a fiber band within a guide element on the weft layer, the band is deformed into a rope. There is no possibility of spreading out this rope again before transfer to the guide hooks. Gaps of irregular width would develop in the border area of the arrangement which would be considered to be substantial quality defects. This mode of operation is therefore not suitable for laying fiber bands of filaments.
DE 100 21 341 A1 describes a similar device. Here additional band fixing systems, the design and operating method of which remain unclear, are assigned to the weft layer instead of to the presser rails. These band fixing systems evidently avoid pushing together the thread sheet during the racking behind the retainer hooks. It is not possible to feed fiber bands of filaments with this arrangement. The swiveling of the strips carrying the guide elements would repeatedly lead to rope formation. Gap-free arrangements of fiber bands cannot be produced in this manner.
Another device was disclosed by DE 102 07 317 C1. The weft thread guide of the weft layer or diagonal layer, which weft guide is aligned parallel to the row of guide hooks, has guide elements, the guide surfaces of which are aligned parallel to the row of guide hooks. The weft thread guide does not perform any movement in the racking direction. The racking is carried out by a standard racking grid which is assigned in the known manner to the retainer needles pointing outwards and upwards.
A guided band is deformed into a rope during racking within the guide elements in the weft layer through the movement of the racking grid—independent of the weft layer. This rope is subsequently inserted into the row of guide hooks and forms the dreaded gaps.
In a further development of DE 101 49 161 C2 discussed initially, the unpublished DE 103 12 534 proposes a modified device with which, i.e., the transfer of the rope-shaped apex of the direction change fold from the fold tensioner to the retainer hooks is to be improved in that a type of fitting (retainer needles distributed on a surface) is provided instead of the row of retainer hooks.
This did not achieve the desired success, either. The device and the control thereof are similarly expensive as was shown in reference to DE 101 49 161 C2. Loose fibers from the fiber band of the direction change fold are also in part guided into the arrangement and undesirable distortions thus occur there.
In another variant of this cited document not published earlier, guide grids that can be activated in a follow-on manner are assigned to the weft layer with its guide elements, which guide grids laterally fix the position of the fiber bands of the upper strand of the direction change fold and align it vertically in a plane parallel to the tips of the guide hooks. The function of the loop holder is here taken over by the fold tensioner which can be pivoted about an axis. This fold tensioner transfers its direction change fold respectively to one individual retainer hook per fiber band. This method of operation is likewise unsatisfactory, since the direction change fold is guided in an uncontrolled manner, in particular during the transfer of the direction change fold from the fold tensioner to the individual retainer hooks. The release of this fold by the fold tensioner leads to the relaxation of fibers and fiber bands in the arrangement.
In view of these seemingly insoluble difficulties in hanging endless fiber bands of filaments into the hooks of the transport chains, attempts have been made to align previously trimmed fiber bands under tension over the two transport chains and to hang them into the rows of the guide hooks of the transport chains. The free ends of the fiber band sections were brought—directed downwards—into a further clamp on the transport chain that was opened again at each laying arrangement before new end sections were inserted. This method of operation has also proven to be very difficult to control. The fiber band filaments not directly connected to the clamp surfaces of the clamps could not be held and tensioned securely. The interaction of the clamps with different functions cannot be controlled under industrial conditions at sufficiently high speed.